Efecto de los surfactantes en el potencial zeta de las suspensiones de nanocelulosa y en la fuerza mecanica de las fibras biocompuestas de nanocelulosa

Abstract

[ES] En este proyecto se va a estudiar cómo afectan diferentes surfactantes no iónicos en la nanocelulosa, concretamente en la nanocelulosa nanofibrada. Se van a estudiar tanto parámetros químicos como mecánicos sobre la interacción de surfactante-nanocelulosa. Entre los parámetros químicos se encuentra el efecto de los surfactantes sobre la superficie de la nanocelulosa que se cuntifica a través del Potencial Zeta, el cual es un indicador para estudiar la estabilidad y otras propiedades electroquímicas de la superficie de las suspensiones de nanopartículas. Por otro lado, se van a realizar pruebas de adsorción para ver en qué medida se están adsorbiendo los surfactantes sobre la nanocelulosa. Estos dos parámetros están relacionados ya que puede que los surfactantes se estén adsorbiendo a la nanocelulosa pero no estén cambiando sus propiedades. Por otro lado se ha llevado a cabo la producción de fibras mediante la extrusión húmeda de la suspensión de nanocelulosa, surfactante y alginato, este último se añade como portador para permitir que la extrusión de las fibras sea continua. Estas fibras se han sometido a pruebas de tracción para determinar propiedades mecánicas como el Módulo de Young, la tenacidad o la tensión máxima que soportan. La característica principal de los surfactantes no iónicos es que el grupo principal hidrófilo no está cargo, este proyecto involucra dos tipos de surfactantes no iónicos, estos son, a base de petróleo y a base de azúcar (naturales).Se han comparado ambos tipos de surfactantes ya que está emergiendo la necesidad de sustituir los surfactantes a base de petróleo que pueden ser tóxicos y además no biodegradables por los naturales que son más amigables con el medioambiente.

[EN] This project involves the use of nanocellulose which has got strong importance in different fields as surface modified materials and nanocomposite materials, due to its attractive properties such as biodegradability, biocompatibility, high strength, high surface area, high tensile modulus, and excellent stiffness among others. Specifically, nanofibrillated cellulose (CNF) extracted from sugar potato pulp has been studied. Also, it is going to use non-ionic surfactants which contain an uncharged hydrophilic head group, surfactants behave as surface-active agents being able to be adsorbed in the CNF surface. Two types of non-ionic surfactants have been tested, these are, petroleum-based and sugar-based, being the main difference between these the origin and the capability to biodegradation. The petroleum-based surfactants have a poor biodegradability and most of them are toxic, for this reason, has emerged the need to replace them, in this case by the sugar-based. So, it is going to be studied the effect of non-ionic surfactants on the zeta potential of CNF and on the mechanical strength of CNF biocomposite fibres. The zeta potential is a parameter that is responsible for studying the stability and electrochemical surface properties of nanoparticle suspensions, and it is based on scattering electrophoretic light technic. Thus, the effect on the zeta potential value has been studied when different concentrations of surfactant are added to a nanocellulose suspension. The measurement of the zeta potential might not make sense if the surfactant was not absorbed in the CNF. For this reason, it will be carried out adsorption test to corroborate whether the surfactant is attaching to the CNF or not. The adsorption has been determined by gravimetric techniques. The second part of the study involves the effect of the surfactant in the mechanical properties of CNF fibres. For this, fibres have been made by the technique of wet spinning in which a suspension of CNF, surfactant, and alginate (carrier polymer) is extruded through a needle immersed in a coagulation bath in which it solidifies for later collection in a rotary drum. To obtain the final fibre, it is necessary to carry out different treatments. Once the fibre is ready, it is subjected to stress test in order to obtain their tensile properties, such as Young s modulus, maximum strain, and fibre strength. To sum up, all of these tests have been carried out for six different surfactants, three based on petroleum and three based on sugar, in order to see the differences that they provide if it were possible to replace the petroleum-based.